NAME

SYNOPSIS

DESCRIPTION

HDF is a multi-object file format that facilitates the transfer of various
types of scientific data between machines and operating systems. Machines currently
supported include the Cray, HP, Vax, Sun, IBM RS/6000, Silicon Graphics,
Macintosh, and IBM PC computers. HDF allows self-definitions of data content
and easy extensibility for future enhancements or compatibility with other
standard formats. HDF includes Fortran and C calling interfaces,and utilities to
prepare raw image of data files or for use with other NCSA software. The HDF
library contains interfaces for storing and retrieving compressed or
uncompressed 8-bit and 24-bit raster images with palettes,
n-Dimensional scientific datasets and binary tables. An interface is
also included that allows arbitray grouping of other HDF objects.

HDF Raster Images

HDF supports the storing of both 8-bit and 24-bit raster images. As well as
storing information about the dimensions and palette of a raster image, HDF
supports raster image compression. In previous versions of HDF, Run-length
encoding and Imcomp compression were both supported. With HDF> 3.3 JPEG
compression is also available.

HDF Scientific Data Sets

Scientific Data Sets (SDSs) are useful for storing n-Dimensional gridded data.
The actual data in the dataset can be of any of the "standard" number types:
8, 16 and 32bit signed and unsigned integers and 32 and 64bit floating point
values. In addition, a certain amount of meta-data can be stored with an
SDS including:

o The coordinate system to use when interpreting or displaying the data.
o Scales to be used for each dimension.
o Labels for each dimension and the dataset as a whole.
o Units for each dimension and the data.
o The valid max and min values for the data.
o Calibration information for the data.
o Fill or missing value information.
o Ability of have more than one file open at a time.
o A more general framework for meta-data within the SDS data-model
(allowing 'name = value' styel meta-data).
o Support for an "unlimited dimension" in the SDS data-model, making
it possible to append planes to an array along one dimension.

HDF Annotations

Any object in an HDF file can have annotations associated with it. There are a
number of types of annotations:

o Labels are assumed to be short strings giving the "name" of a
data object.
o Descriptions are longer text segments that are useful for giving
more indepth information about a data object
o File annotations are assumed to apply to all of the objects in a
single file.

HDF Vset Interfaces

The Vset module provides
interfaces to two basic HDF building blocks. Vgroups are generic grouping
elements allowing a user to associate related objects within an HDF file. As
Vgroups can contain other Vgroups, it is possible to build a hierarchical file.
Vdatas are data structures made up of fields and records. Data is organized into 'fields' within each
Vdata. Each field is identified by a unique 'fieldname'. The type of each
field may be any of the basic number types that HDF supports. Fields of
different types may exist within the same Vdata.

HDF > 3.3 and netCDF

HDF > 3.3 merges in the netCDF library produced by Unidata. The full
netCDF library is supported as is a new "multi-file" SDS interface. Both of
these interfaces can read old netCDF files and HDF files transparently.

EXAMPLES

All HDF routines require the header "hdf.h" to be included in the C
source file. If using the SDS routines the header "mfhdf.h" should be
included instead in in the C source file. Fortran programs should
use "dffunc.inc" and "hdf.inc".

DOCUMENTATION

For the vast majority of users, the "Users Guide" documents and the "Reference"
manuals should be sufficient.

You may download the documentation via ftp on NCSA's anonymous
ftp server. (ftp.ncsa.uiuc.edu:/HDF). On anonymous ftp there the documentation
is available in Postscript, PDF and MIF.

VENDOR

NCSA Software Development Division

Hierarchical Data Format Group

152 Computing Applications Bldg.

605 E. Springfield Ave.

Champaign, IL 61820

VERSION

4.1

LICENSE & SOURCE AVAILABILITY

UNIVERSITY OF ILLINOIS (UI), NATIONAL CENTER FOR SUPERCOMPUTING
APPLICATIONS (NCSA), Software Distribution Policy for Public Domain
Software

NCSA HDF Version 4.1 source code and documentation are in the public
domain, available without fee for education, research, non-commercial and
commercial purposes. Users may distribute the binary or source code to
third parties provided that this statement appears on all copies and that
no charge is made for such copies.

UI MAKES NO REPRESENTATIONS ABOUT THE SUITABILITY OF THE SOFTWARE FOR ANY
PURPOSE. IT IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED WARRANTY. THE
UI SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY THE USER OF THIS
SOFTWARE. The software may have been developed under agreements between
the UI and the Federal Government which entitle the Government to certain
rights.

We ask, but do not require that the following message be include in all
derived works:

Portions developed at the National Center for Supercomputing
Applications at the University of Illinois at Urbana-Champaign.

By copying this program, you, the user, agree to abide by the conditions
and understandings with respect to any software which is marked with a
public domain notice.

Acknowledgements:
----------------

Portions of this software were developed by the Unidata Program at the
University Corporation for Atmospheric Research, specifically the
NETCDF distribution used.

This product also includes software developed by the Independent JPEG
Group, specifically the IJPEG library libjpeg.a.

This product also includes software developed by Jean-loup Gailly
and Mark Adler , specifically the ZLIB library libz.a.

This product includes software developed by the University of
California, Berkeley and its contributors.